The following description relates to adjusting bi-directional damping properties of an in-line passive heave compensator, for example, in an offshore load-handling environment.
During the course of offshore load handling operations by in-line crane-mounted passive heave compensators, requirements for hydraulic damping properties vary for both extend and retract action of the compensator and are based upon the significant wave height. Also, the hydraulic damping properties are typically tailored for different operational circumstances. Therefore, a single or bi-directional fixed hydraulic damping property for extend and retract action of the compensator does not enable optimum efficiency for more than one significant wave height. Installing fixed-area orifices to cause a pressure drop between up-stream and down-stream fluid flows for the extend or retract direction of the compensator to control hydraulic damping will typically not provide the optimum efficiency for a specific range of wave height, for example, where the peak-to-peak wave amplitude difference is large enough.
In-line passive heave compensators are typically transported on pallets or frames. The compensator is separated from the transport frame to prepare the compensator for a working environment. The compensator is typically prepared for operation at one or more separate stations that may include hydraulic fluid storage; nitrogen gas storage; a hydraulic system or pumps to fill and drain the compensator of hydraulic fluid or execute functional and pressure testing of the units; and a nitrogen gas system to charge and discharge gas pressure within the compensator units.